Inorganic fiber paper is lightweight, easy to handle and improved heat resistance, and hence, is used as a heat resisting sealing material, for example. On the other hand, in recent years, a problem has been pointed out that inorganic fibers are inhaled into a human body and the inhaled fibers invade the lung to cause disorders. Under such circumstances, bio-soluble inorganic fibers which do not cause or hardly cause disorders even if inhaled into a human body have been developed (Patent Document 1, identified below, for example).